Sequentially rotate object along two arbitrary axes
I think I may have figured it out...:


frame 1:


use 'child of' constraint to parent object to 1. axis (other object or empty)

frame 60:


rotate axis 1
keyframe object's rot/loc

frame 61:


apply visual transform to object
keyframe constraint factor (1. axis) to 0
keyframe object's rot/loc
add 'child of' constraint to object with 2. axis (other object or empty) as target

frame 120:


rotate axis 2
keyframe object's rot/loc

frame 121:


apply visual transform to object
keyframe constraint factor (2. axis) to 0
keyframe object's rot/loc
add 'child of' constraint to object with 1. axis as target

frame 180:


rotate axis 1
etc.